Process of manufacturing oxids of nitrogen.



0. BEN D BR. PROCESS OF MANUFACTURING OXIDS-0P NITROGEN,

APPLICATION IILE D APILG, 1909. 1,1 1,1 Fig 6/ Patented Dec.5,1911

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. [OOOOOOOOOOOOOOOOO 7' 000000000000000 I I I I I 00000000000000 'r- I II I barren srarss registrar OSCAR BENDER, OF POTSDAM, GERMANY.

PROCESS OF MANUFACTURING OXIIDS 0F NITROGEN.

Specification of Letters Patent.

Fatented 5, full lpplicationfiled April 6, 1909. Serial No. 488,203.

This invention relates to an improved process for manufacturing oxids ofnitrogen.

by oxidizing atmospheric nitrogen at high temperatures produced byburning hydrogen or substantially gaseous or gasified liquid combustiblematerial or fuel such as water gas, illuminating gas, natural gas,methane or petroleum vapors in an atmosphere rich in oxygen.

By means of the present invention in creased yields of oxids of nitrogenare obtained.

Comparative systematic experiments have shown that the oxidation ofatmospheric nitrogen in a flame produced by burning. combustiblematerials -containing hydrogen depends not only on the temperature usedbut also upon a number of other facts which considerably affect theresult and which were hitherto unknown or the importance of which wasnot understood. First I have found that the yield in oxids of nitrogengreatly depends upon the perfect mixing of the combustibles with thegaseous mixtures supplied for combustion, at the moment when the flameis formed. The theoretical reason for this is to be found in the factthat the completion of the reaction between nitrogen and oxygen requiresa measurable interval of time which is scarcely shorter than that whichis at thedisposal of the gases from the commencement of the flamereaction to the end thereof. i When a part of this time is taken up bythe diffusion of the gases infer se, the remainder will be insufficientfor establishing the theoretically possible equilibrium between the oxidof nitrogen and the remaining constituent parts of the burning gases Theyield of oxid of nitrogen will therefore approach more and more thetheoretical yield. the more perfectly the time occupied by the gases inflowing through the flame is utilized for forming the equilibrium' atthe given.

temperature between nitrogen, oxygen, car bon or the remaining materialstaking part in the combustion, This fact had not been taken into accountin the previously known processes of manufacturing oxids of IlllIOr genaccording to which the flame formed by burmng combustible materials issup plied with the other components (air or mixtures of nitrogen andoxygen richer in oxygen than air) by partially forcing them in from theside and partially by blowing them into the same, so that consequentlythe yields remained relatively moderate According to the presentinventionthe perfect mixing of the combustible materials (which has beenrecognized as an important factor).

with the air or with air and oxygen miX- tures during the combustion isobtained in a specially effective manner by dividing the flame intonumerous small pointed flames, the mixing being elfected at thecommencement or first stage in the formation of the flame by supplyingthe required quantity of nitrogen and oxygen to each separate pointedflame to such an extent that the perfect mixing is already completedduring the commencement or first stage in the formation of the flame.Further it was found that in order toobtain the'absolutely necessarycomplete combustion of all the carbon in the combustible or fuel to formcarbonic acid a considerable surplus of oxygen is necessary. It isundesirable to obtain this surplus of oxygen by increasing the supply ofatmospheric air owing to thelarge amount of nitrogen supplied at thesame time which nitrogen is useless and unnecessarily absorbs heat. Itis found however that the cou-ibustion of the finely divided fuel isfacilitated in air enriched with such a quantity of oxygen that themixture contains 50 to per cent. of oxygen and 50 to 10 per cent. ofnitrogen. The quantity of this mixture is preferably such that theproducts of combusion contain 10 to '50 per cent. of free oxygen pervolume by the use of which temperatures of from 1600 to 2500 areobtained in the hottest portion or Zone of the combustion-chamber. Underthose conditions a surprisingly large proportion of nitrogen will beoxidized in the flame.

In order to protectthe oxids from decom-' position which could easilyhappen as is well known. the mixture produced by the reaction'andcontaining in addition to oxid of nitrogen carbonic acid, .free oxygen,

nitrogen, and-the water formed by burning removed at once without beingallowed to return into the combustion chamber. This is done by means ofcooling devices which are arranged immediately adjacent to the reactionzone and which consist preferably of cooled tubes, pipes or the likewhich are so arranged that the water condensed on them is either run offto the outside or collects in a condensation vessel. As the combinationof nitrogen oxid with oxygen can only take place after the separation ofthe Water of condensation, the latter is entirely free, or almost so, ofnitric acid.

The whole process is carried out in a furnace shown diagrammatically inthe accompanying drawings.

Figure 1 is a vertical section thereof and Fig. 2 a horizontal section.

This furnace comprises a casing a lined with fire resisting material. Agrate or burner b, composed of communicating tubular grate-bars, isdisposed horizontally across the lower part ofthe casing. Some one ofsaid bars communicates with an inlet. pipe through which fuel gas isintroduced into all of the bars, and all of the bars are provided withnumerous very-small orifices through which the fuel passes. Asillustrated, small tubes 0 are'mounted over the various orifices of thehollow grate-bars. By this means the combustion of the fuel is forced totake place at the top of said tubes, thus preventing overheating andconsequent rapid wear of the grate-bars. Moreover,

the fuel in passing up the tubes 0 receive an advantageous preliminaryheating preparatory to combustion. The mixture of air and oxygen flowingup through the pipe .9 and between the grate-bars meets the numerousfinely divided jets of fuel gas from the orifices of thegrate-bars orfrom the tubes 0, and thus immediatelyforms a very intimate mixture. Inthe group of flames thus formed above the grate, or burner, theformation of oxid of nitrogen takes place.

The cooling system (1 is arranged beyond the' hottest range or zone pastwhich system the reaction gases flow when leaving the furnace, beingthus cooled and the condensed water formed by the combustion is drainedoff from the condensation vessel or trap, e. The cooled and dryre-action gases are then passed on by the pipe f, in order to be furthertreated so as to form nitric acid or the salts thereof.

It is of course understood that the burner is not restricted to the formdescribed,for instance thenumerous little tubes supplying thecombustible or fuel need not be arranged on a. hollow grate in thefurnace, but may terminate directly in the furnace and supply the airand oxygen mixture through .merous small or pointed flames to which thequantities of nitrogen and oxygen required for obtaining favorableequilibrium conditions are added and thoroughly mixed with the flame atthe commencement or first stage in the formation of the same and furtherby employing an air and oxygen mixture containing 50 to 90 per cent.- ofoxygen in such quantities that the re-action gases contain from 10 to 50per cent. of free oxygen and that by means of an immediate cooling ofthe re-actiongases by cooled pipes or the like, the water ofcondensation formed is drained off. The yield of oxids of nitrogen isincreased tenfold or more as compared with that obtained when employingknown processes.

I claim- 1. The process herein described of producing oxids of nitrogen,which consists in burning combustibles containing hydrogen in a furnacein the form of numerous small pointed flames, supporting the combustionof said flames with a mixture consisting of nitrogen and 50 to of freeoxygen, and condensing the aqueous vapor thus formed.

2. The process herein described of producing oxids of nitrogen, whichconsists in burning a fuel-gas containing hydrogen in the form ofnumerous small pointed flames by passing said fuel-gas through verysmall orifices, supporting the combustion by a mixture of air and oxygencontaining 50 to 90% of oxygen in such proportion that the resultingreaction-gases contain 10 to 50% of free oxygen, and cooling thereaction gases to a temperature below 100 (1., thus condensing the waterformed by the combustion.

In testimony, that I claim the foregoing as my invention, I have signedmy name in presence of two subscribing witnesses.

OSCAR BENDER.

Witnesses:

WOLDEMAR HAUPT, HENRY Hasrnn.

